<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    .box{
        margin:100px auto;
        height: 500px;
        width: 500px;
        background-color: yellow;
        border:1px solid;
    }
    .demo{
        height: 200px;
        width: 200px;
        margin: 50px;
        background-color: black;
    }
</style>
<body>
    <div class="box" id="box">
        <div class="demo" id="demo"></div>
    </div>
</body>
<script>
    var txt ="abcdefghijk";
    console.log(txt.slice(-2));
    var box = document.getElementById("box");
    var demo = document.getElementById("demo");
    console.log(demo.)

</script>
</html>